Conventionally in the field of semiconductor packages and modules, a substrate with a chip cavity utilized for accommodating a semiconductor chip is rather common. The chip cavity consists of a chip cavity inwall and a chip-attached plane. In order to control the height of the chip cavity inwall and the flatness of the chip-attached plane, initially the chip cavity inwall and the chip-attached plane are separately manufactured from different substrates, then the substrate with a chip cavity inwall and the substrate with a chip-attached plane are laminated utilizing an adhesive layer to form a laminated substrate assembly with a chip cavity. As disclosed in U.S. Pat. No. 6,506,626 and U.S. Pat. Application Publication No. 2001/0046725, the substrate with a chip-attached plane is a ball grid array circuit board and the substrate with a chip cavity inwall is a metal stiffener or a spacer circuit board, both substrates are assembled together to be a substrate assembly with a chip cavity for manufacturing a semiconductor package or module with a laminated face-up chip cavity. Also as disclosed in U.S. Pat. No. 6,639,304 and U.S. Pat. No. 6,501,168, the substrate with a chip-attached plane is a metal plate or metal core. Besides, the substrate with a chip cavity inwall is a circuit board with a through opening or a window. Both substrates are assembled together to manufacture semiconductor package or module with face-down chip cavity.
Normally, the adhesive layer applied for laminating the two above-mentioned substrates is acrylate film, liquid adhesive or prepreg. When the adhesive layer is a tape of solid type or gummy type such as acrylate film or prepreg, it is necessary to punch or route an opening in the tape, then the tape is sandwiched between the two substrates to laminate together under the opening of the tape being aligned to the chip-attached plane of the substrate. However, because of the nature of the adhesive tape, the adhesive tape will stick the tools or particles during process, which caused extra problem for cleaning tools and degradation of adhesion. Moreover, the arcylate film is very sensitive to moisture and only can reach JEDEC level four. Furthermore, prepreg may be easily damaged and form in lots of resin flakes or particles during routing or punching process.
When liquid adhesive serves as an adhesive layer to bond the above-mentioned two substrates, it is known that the liquid adhesive needs to apply to the substrate with a chip cavity inwall or to the substrate with a chip-attached plane by means of printing. In order to prevent the adhesive from contaminating the chip cavity inwall during laminating the two substrates, the liquid adhesive must have powerful adhesion with proper surface tension and viscosity. The liquid adhesive will be needed to pass through a pre-bake or drying process after screen printing and then the above-mentioned two substrates are laminated and cured under higher temperatures. However, the curing condition needs to be extremely controlled during curing process, otherwise any mistake may force the liquid adhesive layer to flow to the chip cavity inwall or chip-attached plane and cause the poor flatness for chip attachment.
A method for manufacturing chip cavity on a substrate is disclosed in U.S. Pat. No. 6,195,264. An adhesive layer between the substrate is made of photoimageable material can be interposed between a metal stiffener and a printed circuit board to form a substrate assembly with a chip cavity after lamination, and there is no residual of the adhesive layer in the chip cavity after exposing and developing the photoimageable adhesive layer. However, the requirements for the adhesive layer with photosensitive material should have an excellent photosensitivity and easy photo processing characteristics, moreover, good thermal-setting properties, adhesion, and heat conductivity. However, such kind of adhesive layer with photosensitive material is not easy to get which is in higher cost.